On 11/22/17 8:06 AM, Erik Österlund wrote:
> Hi Dan,
>> On 2017-11-22 13:53, Daniel D. Daugherty wrote:
>> On 11/22/17 4:07 AM, Erik Österlund wrote:
>>> Hi,
>>>>>> Some replies...
>>>>>> On 2017-11-21 17:28, Daniel D. Daugherty wrote:
>>>> Hi Coleen!
>>>>>>>> Thanks for making time to review the Thread-SMR stuff again!!
>>>>>>>> I have added back the other three OpenJDK aliases... This review is
>>>> being done on _four_ different OpenJDK aliases.
>>>>>>>> As always, replies are embedded below...
>>>>>>>>>>>> On 11/20/17 3:12 PM, coleen.phillimore at oracle.com wrote:
>>>>>http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-09-full/src/hotspot/share/runtime/threadSMR.cpp.html>>>>>>>>>>>>>>> 32 ThreadsList::ThreadsList(int entries) : _length(entries),
>>>>> _threads(NEW_C_HEAP_ARRAY(JavaThread*, entries + 1, mtGC)),
>>>>> _next_list(NULL) {
>>>>>>>>>> Seems like it should be mtThread rather than mtGC.
>>>>>>>> Fixed. Definitely an artifact of Erik's original prototype when he
>>>> extracted Thread-SMR from his GC work... Thanks for catching it.
>>>>>>>>>> Confirmed. At the time I considered the Threads list overheads GC
>>> overheads, but I agree mtThread is a better fit today.
>>>>>>>>>>>>>>>>> + return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
>>>>>>>>>> Can you add a comment about where this number came from?
>>>>>>>> I'll have to get that from Erik...
>>>>>> Wow, that looks like code I wrote a *very* long time ago. :) That is
>>> a variation of Knuth's multiplicative hash which is outlined in a
>>> comment in synchronizer.cpp and referred to in that comment as a
>>> phi-based scheme. Basically the magic number is 2^32 * Phi (the
>>> golden ratio), which happens to be a useful value for building a
>>> reasonably simple yet pretty good hash function. It is not the
>>> optimal hash function, but seemed to definitely be good enough for
>>> our purposes.
>>>> So a reasonable comment would be:
>>>> // The literal value is 2^32 * Phi (the golden ratio).
>>>> Yes.
>>> If so, then I'll add it in my wrap up round...
>> Excellent, thanks Dan.
Thanks for confirmation!
Dan
>> /Erik
>>> Dan
>>>>>>>> Thanks,
>>> /Erik
>>>